Fair Value Measurements (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Millions	9 Months Ended	12 Months Ended
Sep. 30, 2011	Dec. 31, 2010
Fair Value, Inputs, Level 1 [Member] \| Restricted marketable securities [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	$ 0	$ 0
Fair Value, Inputs, Level 1 [Member] \| Restricted marketable securities [Member] \| Other long term assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	0	0
June 2009 trading swap [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Assets		0
March 2006 trading swap [Member] \| Fair Value, Inputs, Level 1 [Member] \| Accrued expenses and other current [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Liabilities		0
Fair Value, Inputs, Level 2 [Member] \| Restricted marketable securities [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	20.2	18.2
Fair Value, Inputs, Level 2 [Member] \| Restricted marketable securities [Member] \| Other long term assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	24.9	19.3
June 2009 trading swap [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Assets		1.2
March 2006 trading swap [Member] \| Fair Value, Inputs, Level 2 [Member] \| Accrued expenses and other current [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Liabilities		(12.1)
Fair Value, Inputs, Level 3 [Member] \| Restricted marketable securities [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	0	0
Fair Value, Inputs, Level 3 [Member] \| Restricted marketable securities [Member] \| Other long term assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	0	0
June 2009 trading swap [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Assets		0
March 2006 trading swap [Member] \| Fair Value, Inputs, Level 3 [Member] \| Accrued expenses and other current [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Liabilities		0
Restricted marketable securities [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	20.2	18.2
Fair Value, Assets Measured on Recurring Basis, Investments, Valuation Techniques	M	M
Restricted marketable securities [Member] \| Other long term assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Marketable Securities	24.9	19.3
Fair Value, Assets Measured on Recurring Basis, Investments, Valuation Techniques	M	M
March 2006 trading swap [Member] \| Accrued expenses and other current [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Liabilities		(12.1)
Fair Value, Liabilities Measured on Recurring Basis, Derivative Financial Instruments, Liabilities, Valuation Techniques		I
June 2009 trading swap [Member] \| Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading Swaps, Assets		$ 1.2
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets, Valuation Techniques		I

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

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- Definition

Fair values as of the balance sheet date of all assets resulting from contracts that meet the criteria of being accounted for as derivative instruments, net of the effects of master netting arrangements.

+ References

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-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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This element represents, the inputs and valuation technique(s) used to measure fair value and a discussion of changes in valuation techniques and related inputs, if any, during the period.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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